Double perovskite Ba2BiTaO6 as a promising p-type transparent conductive oxide: A first-principles defect study

The realization of p-type transparent conductive oxides (TCOs) is a long-standing difficulty because of their generally large hole effective mass and low doping limit ascribed to the strong electronegativity of oxygen. By introducing a Bi atom with a lone-pair s orbital on the B site, double perovskite Ba2BiTaO6 could exhibit a dispersive upper valence band and a small hole effective mass due to the strong sp antibonding coupling. In contrast to n-type TCOs, i.e., ZnO and In2O3, first-principles studies on the intrinsic defects of Ba2BiTaO6 show that it is able to exhibit a good p-type property or stay intrinsic instead of being n-type by tuning the chemical potentials and its dominated defects (VBa, VBi, BaBi, and BiTa) are shallow acceptors, indicating that Ba2BiTaO6 is able to be a promising p-type TCO. This work shows that perovskites could be a class of potential p-type TCOs by introducing strong sp coupling with lone-pair-s-orbital elements.